Updated October 2026.
Short answer: the Buck 21ZC and Buck ZC74C are both wood stoves built into a zero-clearance cabinet that frames into a wall, and Buck's 2026 catalog lists the same minimum framing for both. The difference is the firebox inside. The 21ZC is the non-catalytic Model 21 firebox, rated for 800 to 1,800 square feet. The ZC74C is the catalytic Model 74C firebox, rated for 1,500 to 2,600 square feet.
Side by side
| 21ZC | ZC74C | |
|---|---|---|
| Firebox it uses | Model 21 | Model 74C |
| Heats (Buck's rating) | 800-1,800 sq ft | 1,500-2,600 sq ft |
| EPA tested output | 11,079-28,901 BTU/h | 13,300-52,400 BTU/h |
| Firebox volume | 1.6 cu ft | 2.7 cu ft |
| Firewood length | 18" side to side, 11" front to back | 22" side to side, 16" front to back |
| Combustion | Non-catalytic | Catalytic |
| Efficiency | 70 percent | 77 percent |
| Emissions | 1.7 g/h | 1.7 g/h |
| Flue size | 6" | 6" |
| Blower | Included | Included |
| Ash pan | No | Included |
| Weight | 508 lbs | 620 lbs |
| Minimum framing (W x H x D) | 37-1/2" x 35-7/8" x 24-3/4" | 37-1/2" x 35-7/8" x 24-3/4" |
| Mobile home approved | Yes | Yes |
Ratings and framing from the Buck Stove 2026 wood stove catalog. The owner's manual for your unit governs the installation, so confirm every dimension against it before you frame.
What "zero-clearance" means here
A zero-clearance wood stove comes inside its own cabinet, so it frames directly into a wall in new construction or a remodel. You do not need an existing masonry fireplace. That makes the 21ZC and ZC74C the Buck choices when you want the built-in look of a fireplace in a room that does not have one.
If you already have a masonry fireplace, you do not need a zero-clearance stove. The Model 21 and Model 74C use the same fireboxes and install as fireplace inserts with a trim kit.
Which one to choose
- Choose the 21ZC for a smaller home or one zone of a larger one, up to about 1,800 square feet. It is non-catalytic, so there is no combustor to inspect or replace.
- Choose the ZC74C for 1,500 to 2,600 square feet, or when you want longer burns. Its firebox holds about 70 percent more wood (2.7 against 1.6 cubic feet), it takes 22" logs, and its catalytic combustor brings efficiency to 77 percent. It also adds an ash pan.
- In the overlap (1,500 to 1,800 square feet): lean toward the ZC74C for a drafty older house or for heat through the night, and toward the 21ZC for a tight, well-insulated house you heat mostly in the evenings.
Planning the install
- Framing: Buck's 2026 catalog lists a minimum framed opening of 37-1/2" W x 35-7/8" H x 24-3/4" D for both. For the ZC74C, it lists front clearances of 30-1/2" to a mantel and 26" to a sidewall.
- Hearth extension: Buck's 51ZC cabinet manual (the cabinet manual supplied with the 21ZC) calls for a hearth extension at least 16" deep in front of the cabinet and at least 37-1/2" wide. For the ZC74C, confirm this carries over in the manual for its cabinet.
- Power: the 51ZC cabinet manual calls for a dedicated 15 amp circuit for the blower. For the ZC74C, confirm this in the manual for its cabinet. Plan the electrical run before the wall is closed.
- Venting: both use a 6" flue. Follow the owner's manual for the chimney system and the clearances it requires.
- Local rules: check with your local building department about permits and inspection before you start.
The Buck 51ZC cabinet manual (January 2024) is linked on both product pages. Confirm its figures against the manual for the unit you buy.
Questions buyers ask
Can I put a 21ZC or ZC74C in my existing fireplace?
They are made to frame into a wall. For an existing masonry fireplace, use the Model 21 or Model 74C as an insert instead.
Is the blower included?
Yes, on both. Buck's 51ZC cabinet manual calls for its own 15 amp circuit.
Do they need an ash pan?
The ZC74C includes one. The 21ZC does not have one.
Does the federal tax credit apply?
No. The federal credit ended for stoves placed in service after December 31, 2025. Read more about the tax credit.
What about the rest of the Buck line?
Our Buck Stove sizing guide compares Buck's 2026 wood heating stoves, from the Model 21 to the Model 91.
Before you order
Both stoves ship free by freight from MyBBQDirect within the continental US, and the carrier calls ahead to schedule delivery. Each product page has the delivery details. Framing a wall for a zero-clearance stove is easier to get right before you build, so call (708) 765-6925 with your room size and wall plan and we will check the numbers with you.
